Western Wallflower

Erysimum capitatum

yellow flowers in field
Central Basin, south side | March 2016

Western wallflower (Erysimum capitatum) is a bright-yellow, spring-blooming plant that is native throughout western North America from Alaska to northern Mexico and from alpine meadows to desert canyons.

Western wallflower is one of our few native members of the mustard family (Brassicaceae), a family better known for its crop plants, like cabbage and broccoli, and for its troublesome invasive plants such as black mustard and wild radish.

The name “wallflower” seems inappropriate for this bold, beautiful flower. In fact, it was named after a European relative that often grows from and around old stone walls.

Other Common Names:

coast wallflower, Douglas' wallflower, sanddune wallflower, prairie rocket

Description 4,23,59

Western wallflower is a widespread and variable biennial or short-lived perennial herb. A basal rosette of linear leaves develops from a taproot the first year. The next year, this produces one or a few upright stems with ascending side branches, usually less than four feet (115 cm) tall. Leaves are linear to narrowly lanceolate or oblanceolate. The basal leaves have short petioles and the blades may reach ten inches (25 cm) long but are usually smaller. Cauline leaves lack the petioles and decrease in size upward. Leaves are dull green with a pale midvein and smooth or somewhat toothed margins. Most parts of the plant are covered with very small hairs that are attached at the midpoint rather than at one end (T-shaped); these are difficult to see with the unaided eye, but they give the leaves a slightly roughened texture.

Flowers are produced in cylindrical clusters at the branch ends. The clusters elongate as flowers mature and fruits develop. The youngest flowers are uppermost and on the same level as the developing buds, giving the cluster a flat-topped look. Each flower has four sepals, in two pairs of slightly different size and shape. There are four petals that are usually yellow to orange but may also be red, purple or blue.114  Local plants are bright yellow. Petals have basal claws, concealed by the sepals, and conspicuous, rounded outer limbs. There are six stamens, two shorter than the others; the anthers curl backward after the pollen has been released. There is one pistil with a straight-sided, superior two-chambered ovary, a short style, and a two-lobed, capitate stigma. The main bloom time is March – July;1 our blooms usually peak in March and April.

The fruit is a long, thin, four-sided seedpod (a silique), that splits open lengthwise from the bottom, exposing two rows of small brown seeds attached to a central membrane.

Red stem with tried out leaf revealing seeds

Valves of seed pod open from bottom revealing seeds attached to central membrane | Central Basin | May 2016

Yellow flowers

Central Basin, east end | March 2016

Green stems with long leaves

Central Basin, east end | March 2016

Distribution 7,59,252

Western wallflower is a California native that is widespread in the western United States and northern Mexico; it has been introduced into New England.114 It occurs throughout California except for the Central Valley and Imperial County.

It is adapted to a variety of habitats and vegetation types, from alpine meadows to desert canyons, generally below 10,000 feet (3100 m). It is often found in rocky, clay or sandy open areas.

In the Reserve, western wallflower can be seen in Central Basin in the north-facing open areas above the main trail.

Classification 2,11,44,143

Western wallflower is dicot angiosperm in the mustard family (Brassicaceae), a family of major economic importance that has very broad distribution. There are many well-known species and cultivars in the family including common vegetable crops such as cabbage, cauliflower, broccoli, turnips, watercress and radish, and ornamentals such as sweet alyssum and stock; there are also invasive weeds such as black mustard, wild radish, and sea rocket. Interestingly, six of our common vegetables–cabbage, cauliflower, kohlrabi, Brussels sprouts, broccoli, and kale–were all bred from a single species of mustard, Brassica oleracea.143

Members of the mustard family are characterized by four petals in a cross shape (from which came the former family name Cruciferae, or cross-bearing); and by six stamens, four long and two short. Mustard seedpods come in different shapes. When mature, they split open from both sides, exposing the seeds on a central membrane. Seedpods occur radially around the flower stalk, “like a spiral staircase for the little people.”143

Sixteen species in the mustard family have been reported from the Reserve.48 Eight of these are non-native weeds, including black mustard and field mustard (Brassica nigra and B. rapa), wild radish (Raphanus sativus), sea rocket (Cakile maritima) and stock (Matthiola incana). Others include lovely spring natives such as milkmaids (Cardamine californica).

There is uncertainty about the taxonomy of western wallflower. Some researchers would place E. capitatum and the closely related E. asperum into a single species.253  A number of subspecies and varieties of E. capitatum have been proposed. At present, CalFlora7 recognizes four in California, three of which have very restricted distributions. Jepson recognizes only two. According to the location, ours is likely to be variety capitata,48 which is the most widespread of the varieties and the only one reported from this area.

Alternate Scientific Names:

Erysimum arkansanum, Erysimum alatum

Jepson eFlora Taxon Page
Yellow flowers growing by brown fallen tree

Central Basin, east end | March 2016

yellow flowers

Central basin, east end | March 2016

Yellow flowers growing in fields

Central Basin, east end | March 2016

Ecology 41,254

Western wallflower is a pollinator-generalist,255 a plant that is pollinated by a large variety of organisms; such plants have flowers that are not adapted either to attract or to exclude any type of insect. The advantage of being a pollinator-generalist is that it provides reproductive security especially when pollinator populations are low or fluctuate widely. Thus, a pollinator-generalist may be more easily able to disperse into other habitats or to survive in extreme habitats. In contrast, a plant with flowers adapted for one or a few pollinators (yuccas are an extreme example) may more efficiently distribute its pollen, since the pollinators are more likely to visit a plant of the same species.

The relationship between a flower and its pollinator (or pollinators) is thought to be a driving force in flower adaptation, diversification, and evolution. Several such studies have focused on Erysimum species and their pollinators,255, 256 but all of the studies are beyond the scope of this discussion.

yellow flowers with four petals

Central Basin | March 2016

Green stem and yellow flower

Central Basin, east end | March 2016

Yellow flowers in field

Central Basin, south side | March 2016

Human Uses 114

We have found no reports that western wallflower was used by local Native Americans. Elsewhere in North America, a variety of medicinal uses have been recorded, including treatments for nasal congestion, toothache and muscle soreness; also flowers have been used to make a yellow dye.

yellow flowers in field

Central Basin, south side | March 2011

yellow flower

Central Basin, south side | March 2012

Yellow flowers growing on hill

Central Basin, south side | March 2014

Interesting Facts 59,252

“Wall flower” seems an unlikely name for this bold, showy plant. In truth, it was named for a similar European relative that commonly grows on or near old stone fences and walls.

yellow flowers with four petals

Central Basin | March 2016

yellow flowers in field

Central Basin, east end | March 2016

yellow flowers

Central Basin, east end | March 2016

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